Add license file

Author: GetoXs

src/MediatR.Extensions.FluentValidation.AspNetCore.sln

@@ -16,6 +16,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "workflows", "workflows", "{
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{5B03E2AC-3064-4A2C-B610-24F378EE82D2}"
 	ProjectSection(SolutionItems) = preProject
+		..\LICENSE = ..\LICENSE
 		..\README.md = ..\README.md
 	EndProjectSection
 EndProject